You will need to unbolt the 6 bolts holding on the actual steel bumper.
The hitch will sandwich itself inbetween the car and the bumper with these 6 large bolts.

I opened mine yesterday and looked at the instructions - the instuctions make it seem like you don't need to unbolt the bumper beam, but it makes a lot more sense to put it between the bumper and the chassis.

I ran the trailer lights wiring thru the grommet on the right just below the taillight.
I used a wiring kit MODULITE 119190. $75 at my local trailer store.
It is powered directly from the cars battery and tab into the tail lights to get signal. I was hoping this would keep my LIGHT out warning to not happen..but it does register light out all the time..oh well.
all lights work and im not pulling power thru the taillight harness so its fine.

I got a Modulite as well. What wires did you tap into (there appear to be a couple of bulbs that light up for brake)? And the tail lights just seem to be power to the LED/fiberoptic type lights in the tail light assembly.

Here is what I could find that I think will work:

Left side of the car in multibulb assembly wires:
Left Turn: Blue wire with green stripe
Brakes: Purple with Yellow stripe

Left side of the car on Tail light bulb harness:
Tail Light: Purple wire with Light Blue stripe

Right side of the car in multibulb assembly:
Right Turn: Blue wire with Brown stripe

I assume the "bulbs out" occurs when the trailer lights are connected. If not, I do not know how to "fix it". If my guess is correct and it's only when the lights are connected, you might try changing the jet ski trailer to led lights. I have them on my boat and like them better for a couple reasons. First, they do not corrode and loose the contact when the trailer sit unused. Second, they draw very little power. Third they do not get hot so nothing bad happens if you do not disconnect them before dunking them in the lake.

Even though your setup is not supposed to take it's power from the light circuit, my guess is that it is to some degree and dropping back a lot on the current may eliminate the bulb out signal. Even if it does not, the led lights have advantages.

I just used a cheap set from harbor freight. They were $40 or less. They work fine.

Yea my BULB out light is on most all the time now.. but oh well..
even after the $75 modulite kit.. I was hoping the system would be fooled into thinking the system was OK... but BMW has fine tolerances in this case.

- powder coated the tire rack uprights
- added safety chains
- pumped up tires to 60 psi
- added DOT reflective tape
- tidied up the wiring
- new smaller, current looking tail lights
- added a spare tire mount on the front (spare tire to come) - had to mount it horizontally because of the tire rack up front. At least until I get the 6" hitch extender.

I'll just add some eyebolts around the perimeter to tie stuff down to and she'll be awesome on the drive from HB to Atlanta and back.